Stacking and retrieving system and method

ABSTRACT

A stacking and retrieving system for stockpiles of material wherein a self-propelled retrieving machine cooperates with the self-propelled stacker in retrieving material, the speed of the stacker being controlled to conform to that of the retrieving machine, while steering of the retrieving machine is controlled for movement parallel to the path of the stacker.

United States Patent [72] Inventor Fred T. Smith Aurora, 111.

[21] Appl. No. 838,284

[22] Filed July 1, 1969 [45] Patented Nov. 23, 1971 [73] AssigneeBarber-Greene Company Aurora, 111.

[54] STACKING AND RETRlEVlNG SYSTEM AND METHOD 7 Claims, 9 Drawing Figs.

[52] US. Cl 198/36, 214/10,114/152 [51] Int. Cl B65g61/00 [50] Field ofSearch 214/10, 152; '1 98/36 [56] References Cited UNITED STATES PATENTS2,734,642 2/1956 Mercier 214/10 2,781,890 2/1957 Mercier 198/36 X3,393,791 7/1968 Heitzer 198/36 FOREIGN PATENTS 1,002,504 8/1965 GreatBritain 214/10 Primary Examiner- Assistant Examiner-Frarik E. WernerAttorney-H111, Sherman, Meroni, Gross & Simpson ABSTRACT: A stacking andretrieving system for stockpiles of material wherein a self-propelledretrieving machine cooperates with the self-propelled stacker inretrieving material, the speed of the stacker being controlled toconform to that of the retrieving machine, while steering of theretrieving machine is controlled for movement parallel to the path ofthe stacker.

PATENTEDuuv 2 3 Ian SHEET 1 BF 6 STACKING AND RETRIEVING SYSTEM ANDMETHOD SUMMARY OF THE INVENTION This invention relates to a stacking andretrieving system and method and particularly to a retrieving systemand,

method utilizing the stacker which initially produces the stockpile as apart of the retrieving system along with a separate self-propelledretrieving machine.

An object of the invention is to provide a stacking and retrievingsystem and method providing improved efficiency.

A further object of the present invention is to provide an improvedapparatus and method for retrieving material from stockpiles or thelike.

A particular feature of the present invention resides in the provisionof a stacking and retrieving system which utilizes a separableretrieving machine such as a multiwheeled selfpropelledmaterial-handling machine, whereby a stacker with a relativelylightweight boom is operable independently of the material-handlingmachine during transfer of material to a stockpile, but is operativelyassociated with such machine for retrieving material from the stockpilewith optimum speed and efficiency. The material-handling machine can bea relatively heavy piece of equipment with multiple relatively rigidmaterial retrieving wheels for very fast and efficient retrieving ofmaterial as the machine moves longitudinally of the stockpile at asteady speed.

Other objects, features and advantages of the invention will be readilyapparent from the following description of a certain preferredembodiment thereof, taken in conjunction with the accompanying drawings,although variations and modifications may be effected without departingfrom the spirit and scope of the novel concepts of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary somewhatdiagrammatic plan view of a stacking and retrieving system in accordancewith the present invention;

FIG. 2 is a schematic side elevational view of the system of FIG. 1showing a retrieving machine and stacker in cooperating relationshipduring a material retrieving operation;

FIG. 3 is a somewhat diagrammatic partial elevational view illustratingthe system of the present invention operating in stacking mode;

FIG. 4 is a somewhat diagrammatic transverse sectional view showing thestacker of FIG. 3 operating in the stacking mode;

FIG. 5 is an enlarged partial side elevational view showing furtherdetails of the stacker system of the present invention with the stackeroperating to retrieve material from a stockpile;

FIG. 6 is an enlarged partial somewhat diagrammatic. side elevationalview showing further details of the system of FIG. 1 operating inretrieving mode;

FIG. 7 is a further enlarged partial side elevational view showing thecooperating probe devices of the retrieving machine and stacker of thesystem of FIG. 1;

FIG. 8 is an enlarged diagrammatic partial plan view illustrating theoperation of the probe structure of FIG. 7; and

FIG. 9 is an enlarged partial sectional view showing certain details ofconstruction of the vertical probe structure carried by the stacker inthe illustrated system.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates an overallview of a stacking and reclaiming system in accordance with the presentinvention wherein an overland conveyor 10 supplies material to thesystem from a source of supply, such as a coal mining operation. Aconventional transfer tower 11 may receive material from the conveyor l0and deliver it selectively to one of two belt line conveyors l2 and 13which serve to'convey the material in the direction indicated by arrowsI4 and 15. The material carried by conveyor 12 may be supplied to aself-propelled stacker 18, while the material carried by the conveyor 13may be supplied to a stacker indicated at 19.

The stackers l8 and 19 may be of identical construction and may operatealong common longitudinal rails indicated at 22 and 23. The stacker 18is illustrated as having an elevator conveyor assembly 26 associatedtherewith including a tripper section 27, a transfer section 28 and anelevator conveyor section 29. Each of the stackers is provided with aboom conveyor structure, the boom of stacker 18 being indicated at 36,and the boom of stacker 19 being indicated at 37.

For transferring material from the belt line conveyors 12 and 13 tostockpile regions such as indicated at 38 and 39, the boom of thestacker 18 or 19 is held in a relatively elevated position as indicatedin FIG. 4 for boom 36. The boom conveyor such as indicated at 42 thenoperates in the direction of arrow 43 to deposit material centrally ofthe stockpile region 38 so as to produce a stockpile such as indicatedat 44 in FIG. 4. By rotating the tower 46 of stacker I8 through 180',the boom conveyor 42 may supply material to stockpile reg'on 39 so as tobuild up a stockpile as indicated at 47 in FIG. 4.

The stacker 19 being identical to the stacker 18 may perform the samefunctions as illustrated in FIG. 4. Since the slackers l8 and 19 andconveyor assemblies 26 and 30 may be identical, in general only one willbe described specifically herein, and it will beunderstood that suchdescription will also be applicable to the other identical component.

Refen'ing to FIG. 3, it will be observed that material moving in thedirection of arrow 14 on conveyor 12 is removed from the conveyor 12 bymeans of the tripper section 27 whose tripper conveyor is operating inthe direction of arrow 60. Material discharged by the tripper conveyorinto a chute 61 of transfer section 28. From the chute 61, the.materialcan be delivered to a branching chute 62 or 63. The chute 62 suppliesthe material to elevator conveyor 64 of conveyor section 29 whichoperates in the direction of arrow 65. Alternatively, the material maybe returned to conveyor 12 via chute 63. The tail pulley of conveyor 64is indicated at 70 and material is discharged from conveyor 64 asindicated by arrow 71 so as to be supplied to a hopper 72, also seen inFIG. 4. The material flows from the hopper 72 to a delivery chute 75,FIG. 4, so as to be supplied as indicated by arrow 76 to the boomconveyor 42, FIG. 4, operating in the direction of arrow 43. Thedischarge of material from the end of the boom material is indicated byarrow 77.

Referring to FIG. 3, it will be observed that the stacker I8 issupported on the rails such as 22 by means of wheels such as indicatedat 80. The elevator conveyor assembly 26 is similarly supported by meansof wheels such as indicated at 81-84 so as to be movable with thestacker 18 as the stacker moves along the length of the stockpileregions 38 and 39, FIG. I, to distribute material to one of thestockpiles such as stockpiles 44 indicated in FIG. 4. When the stackeris to operate in a reclaiming mode, the elevator conveyor assembly 26may be shifted to the position indicated in dash outline at 26' in FIG.3, the corresponding location of tail pulley 70 being indicated at 70',and the corresponding position of wheel 81 being indicated at 81'. Inthe detached position 26, the transfer section 28 may receive materialfrom the tripper 27 and supply it to the chute 63, so that material issimply picked up from conveyor 12 at location 86 and deposited on theconveyor again at a location such as indicated at 87 in FIG. 3. FIG. 4may be considered as a view of the stacker 18 with the elevator assembly26 disengaged therefrom. During stacking mode, the conveyor assembly 26may be secured for joint movement with the stacker 18 in eitherdirection of movement of the stacker along the rails 22 and 23, theconveyor assembly being driven along the rails 22 and 23 by means of thepropulsion mechanism for the stacker 18. The stacker-propellinghydraulic power pack is located generally at the region 88 and includesa drive for driving the wheel 89 and also the wheel 90 of the stacker.The stacker may also be provided with a boom hoist drive locatedgenerally in the region 92; FIG. 4. The operator s cab may be located atthe region indicated at 93in FIG. 4 so as to face in the direction ofextension of the boom 36.

nnnn n By way of example, in one installation, stacker 18 was operativeto stock a south stockpile such as 44 or a north stockpile such as 47over the entire length thereof from the extreme west boundary (at theleft as viewed in FIG. 1) to within 400 feet of the extreme eastboundary (at the right as viewed in FIG. 1). Similarly the stacker suchas indicated at 19 was selectively operable to stock the stockpiles 44and 47 over the length thereof extending from the extreme east boundaryto within 400 feet of the extreme west boundary of the stockpiles.Suitable limit switches or the like are provided to insure againstcollision, but this forms no part of the present invention and is notillustrated herein, the provision of such means being well within theskill of the art.

Referring to FIG. 4, it will be understood that the boom 36 is pivotallymounted at the stacker 18 so as to enable the discharge end thereof at77 to be raised or lowered by means of a cable comparable to the cableindicated at 100 for the stacker 19 in FIG. 2. Conventional hoist meansis, of course, provided for raising and lowering the boom of eachstacker, and also for rotating the boom-supporting tower such as 46,FIG. 4, about a central vertical axis. All such means as well as thedetailed construction and control of the various conveyors, chutes, andthe like form no part of the present invention, and are obviously fullywithin the skill of the art.

The stackers 18 and 19 are each capable of cooperating with amaterial-handling machine generally indicated at 120, FIG. 2, inreclaiming material from the stockpiles 44 and 47 over the previouslymentioned operating ranges thereof. The stacker 19 has been illustratedin FIGS. 1 and 2 as cooperating with the material-handling machine 120for reclaiming material from the stockpile 47, by way of example. Thematerial handling machine 120 is a self-propelled machine for examplehaving a three point suspension of caterpillar-type treads including aforward steerable tread 121 and a pair of rear treads 122 and 123 (FIG.6.) The machine is shown as including two relatively rigid materialretrieving or digging wheels 133 and 134 which are driven by the powerplant of the machine 120 so as to scoop up material from the stockpileand to supply the same to an internal conveyor 136 extendingtransversely into the digging wheels I33 and 134 and operating to movematerial in the direction of arrow 137 onto a second or reclaimerconveyor 140 which is carried by a reclaimer boom 142. The boom 142 ispivotally carried by the machine 120, and its height may be controlledby means of a cable 143. The operator cab for the machine may be locatedat 144 so that the operator can view the progress of the machine alongthe stockpile and steer the machine 120 so that it moves substantiallyparallel to the rails 22 and 23 along which the stacker 19 moves.Reclaimed material is moved by the conveyor 140 in the direction ofarrow 146 to a discharge chute or region 147 which is maintained inalignment with a receiving chute or region I48 carried on the boom 37.In this mode of operation, the stacker boom conveyor 150 similar toconveyor 42 operates in the direction of arrow so as to move materialfrom the receiving chute 148 to a discharge region or point indicated byan arrow 152 adjacent a tail pulley 153 of the conveyor. In FIG. 1, itwill be observed that the stacker boom 37 may be swung about a verticalaxis so as to accommodate different spacings between the reclaimer 120and stacker 19 as the reclaimer makes successive passes along the lengthof the stockpiles such as 47.

Referring to FIG. 5, an arrangement of material transfer chutes 161-163serves to convey material as indicated by arrows I64 and 165 to a crossfeed conveyor 166 and moving material in the direction of arrow 167. Amaterial discharge chute 170 then serves to direct material as indicatedby arrow 171 on to the conveyor 12 which then transports the material tothe east transfer station 180. From the transfer station 180 materialmay be moved in the direction of arrow 181 via a conveyor 182 which in aparticular installation led to a barge loading clock. In the actualinstallation, a further conveyor 184 was provided for conveying materialfrom the transfer station 180 in the direction of arrow 185. The furtherdetails of the stacker 19 may be similar to those illustrated for thestacker 18, and of course, the stacker 18 would also be provided withthe components illustrated in FIG. 5 for the stacker 19. The reversibledrive for the stacker boom conveyors and other details are, of course,well within the skill of those skilled in the present art.

Referring to FIG. 6, it will be observed that the boom 142 of thereclaiming machine has at the end thereof a series of frame members201-204 which are integral with the frame of the boom 142. Similarly theboom 37 of the stacker 19 carries certain frame members such asindicated at 211-215 integral therewith. The members 201-204 togetherwith similar members 221-224, FIG. 8, on the opposite side of thereclaimer boom 142, FIG. 7, mounting horizontally extending members 225and 226, FIG. 8. As seen in FIG. 7, the frame members 211-215 of thestacker boom 37 mount a horizontal plate 231 which in turn carries asubstantially vertically disposed probe means 233. As best seen in FIG.8, cooperating probe means carried on the reclaimer parts 225 and 226comprise a longitudinal error-sensing arm 240 and a transverseerror-sensing arm 241.

The sensing arm 240 is pivotally mounted at 244 on the horizontal member225 and is spring urged in the clockwise direction as viewed in FIG. 8by means of a tension spring 245, so that the arm 240 will be held inengagement with the probe 233 over the operating range of positions ofthe sensing arm 240 as determined by stop bars 247 and 248, FIG. 8. Thusthe sensing arm 240 is capable of a range of pivotal movement from theextreme counterclockwise position indicated at 240-1 in dash outline inFIG. 8 to the extreme clockwise position indicated in dot dash outlineat 240-2 in FIG. 8. For sensing the angular movement of the sensing arm240 as it follows the position of the probe 233 within its operatingrange, a transducer device 250 is provided having a movable rod 251thereof pivotally connected at 252 with a suitable point on the sensingarm 240. By way of example, the point of connection may be such relativeto the pivot point 244 that the rod 251 reciprocates over a range ofplus or minus 0.5 inch from the central position of the sensing arm 240shown in solid outline in FIG. 8. Any suitable transducer device may beutilized, for example a transducer for supplying an electric signalwhose polarity is positive or minus depending on the direction of theerror from the central position of the sensing arm 240 and providing anelectric potential whose magnitude is a function of the amount ofdisplacement of the rod 251 from its central position which is actuallyshown in FIG. 8.

Similarly the transverse sensing arm 241 is pivotally mounted at 264 andis spring urged by means of tension spring 265 in the counterclockwisedirection as viewed in FIG. 8 so as to maintain the sensing arm 241 inengagement with the probe 233 over the operating range of positions ofthe sensing arm 241 between stop members 267 and 268. The extremecounterclockwise position of sensing arm 241 is indicated at 241-1 indash outline, while the extreme clockwise position of the sensing arm241 is indicated at 241-2 in dot dash outline. A transducer 270 isprovided having its rod 271 pivotally connected at 272 with the sensingam 241 so that the transducer 270 supplies any desired error signal suchas the electrical error signal described with reference to thetransducer 250.

FIG. 9 illustrates the details of probe means 233, from which it will benoted that the probe means 233 comprises a tube 280 having an integralend wall 281 with an aperture therein through which a cable 282 freelyextends. The cable 282 has washer means 283 retained at the end thereofby means of a fitting 284 which is fixedly secured to the end of thecable. A compression spring 285 is sitted at its upper end against theend wall 281 and acts against the washer means 283 to urge the washermeans downwardly and thus to maintain the cable 282 taut, the oppositeend of the cable at 286 being fixedly secured by means of a fastener 287to an integral leg 231a ofthe plate 231.

The fastening means 287 is so adjusted that the spring 285 is under asubstantial compression such as to relatively strongly resist deflectionof the rod 233 from its vertical orientation illustrated in FIG. 9.Thus, the force of the tension springs 245 and 265 is insufiicient todeflect the probe 233 from its vertical orientation, and the transducers250 and 270 will accurately reflect the relationship between the stackerand reclaimer so long as the sensing arms 240 and 241 remain withintheir operating range as illustrated in FIG. 8. If however the reclaimeris advanced in the longitudinal direction indicated by arrow 290 so thatthe sensing arm 240 is moved in the counterclockwise direction againstthe stop 248, and the reclaimer continues to advance relative to thestacker, the probe 233 will deflect out of its vertical orientationagainst the action of spring 285 to a sufficient extent to allow thesensing arm 240 to move past the location of the probe 233. Similarly ifthe reclaiming machine should move toward the stacker in the transversedirection indicated by arrow 291, the probe means 233 would be deflectedin the direction of arrow 292 in FIG. 9 and would not be damaged byovertravel of the reclaimer toward the stacker. The manner in which theprobe 233 pivots to yield is indicated in dash outline at 233', FIG. 9.

The specific electric circuitry utilized in conjunction with thetransducers250 and 270 forms no part of the present invention and isentirely within the skill of workers in the relevant art. Electricalcables are indicated at 301 and 302 leading from the transducers 250 and270 to a suitable error signal transmission circuit 303 which has anoutput cable at 304 leading via the boom 142 to the control cab 144 ofthe reclaimer. Simply by way of example, at the control cab, thelongitudinal and transverse errors sensed by the transducers 250 and 270may be visually displayed so that the operator of the reclaiming machinecan steer the reclaimer so as to maintain an essentially minimumtransverse error in the relationship between the reclaimer and stacker,that is, maintaining a position of the sensing arm 241 relative to theprobe means 233 as represented by the solid outline position of thesensing arm 241 in FIG. 8. Similarly, any longitudinal error may betransmitted by means of a cable 305 to the control cab of the stacker 19so as to enable the operator of the stacker to maintain any longitudinalerror at a minimum, that is to maintain the probe 233 in the positionillustrated in FIG. 8 relative to the central position of the sensingarm shown in solid outline at 240 in FIG. 8. The remote indicators maysimply take the form of movable pointers which move over relativelysubstantial distances in opposite directions from a central zero errorposition. In FIG. 6, cable 305 has been indicated diagrammatically asincluding a plug element at 306 for detachable engagement with areceptacle on the boom 37, the boom 37 then having suitable cable meansfor transmitting the longitudinal error signal to the cab of thestacker.

Of course, it is well within the skill of the art to provide automaticelectric-hydraulic controls so that the speed of the stacker 19 isautomatically controlled to maintain a substantially zero longitudinalerror from transducer 250, and similar automatic controls can readily beapplied to the steering from the material handling machine 120 so as tomaintain a minimum transverse error signal from the transducer 270.Simply by way of example, such controls are available from theMinneapolis-Honeywell Company. Typical transducers supplied byMinneapolis-Honeywell Company are identified as LVDT transducers. Thematerial-handling machine 120 may conform with a two wheel excavatormachine disclosed in my copending US. Pat. application entitledMulti-Wheeled Material Handling Device," U.S. Ser. No. 668,064, filedSept. 15, I967 which issued on Mar. 17, 1970 as US. Pat. No. 3,500,563.

SUMMARY OF OPERATION In carrying out a reclaiming operation, thematerial-handling machine 120 is moved under manual control to thebeginning of a longitudinal pass along the length of a stockpile such as47, FIG. 1. A stacker such as indicated at 19 is positioned adjacent thematerial-handling machine 120 with the stacker boom 37 lowered and itsmaterial-receiving hopper 148 positioned beneath the discharge 147 ofthe reclaimer boom 142. As illustrated in FIG. 1, when the stacker 19and reclaimer are relatively close, the boom 37 is swung so as to extendbehind the stacker at an acute angle to the direction of rails 22 and23. At each successive pass of the materialretrieving machine 120, themachine is moved further in the transverse direction from the stackerl9, and the boom 37 is swung toward the machine 120 to maintain theoperating relationship thereof as illustrated in FIG. 2. As seen inFIGS. 2 and 6 the material-retrieving machine 120 is moved into aposition such that its longitudinal sensing arm 240 is in contact withthe vertically depending probe or reference member 233, with the sensingarm 240 disposed substantially at its central zero error position shownin solid outline in FIG. 8. Similarly, the boom 37 is fixed at an anglesuch that the transverse error-sensing arm 241 is in engagement with theprobe 233, FIG. 8, and is maintained thereby in the central zero errorposition.

As the material-retrieving machine 120 starts to move down the stockpile47, the physical movement of the hand control within the cab of theretrieving machine may signal the hydrostatic transmission of thestacker 19 to move ahead at approximately the same speed as thereclaimer. The cable 305, FIG. 2, may include suitable electricalconductors for carrying out this function, or the stacker may be simplycontrolled by an operator in its cab to startup at the same time as theretrieving machine. The hydrostatic transmission of the stacker 19 wouldbe driving the stacker wheels such as those indicated at 312 and 313,FIG. 2. If the retrieving machine 120 starts to move ahead a littlefaster than the stacker, then the transducer 250, FIG. 8, is displacedto produce a longitudinal error signal of magnitude and polarity inaccordance with such error. This error may be utilized for manual orautomatic correction as previously described so as to correspondinglyincrease the speed of the hydrostatic transmission on the stacker. Asthe stacker speed matches the speed of the retrieving machine, thetransducer 250 would return to its neutral or zero error position asshown in FIG. 8, and the new stacker speed would be the same as thespeed of the retrieving machine. In steering if the retrieving machinegets too close to the stacker, the sensing arm 241 would be rotated inthe clockwise direction to produce a transverse error signal from thetransducer 270 of magnitude and polarity in accordance with the error.The steering cylinders of the retrieving machine would then be actuatedeither manually or automatically to direct the front crawler 121, FIG.2, of the retrieving machine 120 so as to steer the machine away fromthe stacker until the proper distance therebetween is reestablished. Atthe proper transverse distance, the transducer 270 returns to the zeroerror position shown in FIG. 8, and the material retrieving machine isthen moving parallel to the tracks 22, 23, FIG. 2 on which the stackertravels. Thus, the stacker I9 is slaved to the retrieving machine 120 sofar as speed of motion is concerned, and the retrieving machine 120 isslaved to the stacker so as to maintain a predetermined distancetherebetween, the steering of the retrieving machine being controlled tomaintain the predetermined distance. The result is that during areclaiming pass, material picked up by the wheels 133, 134, FIG. 2, istransported as indicated by arrows 138, 146 and 314 into the centralportion of the receiving hopper 148, FIG. 2, at the end of the stackerboom 37. From there, thematerial is transported by the stacker conveyor42 as indicated by arrows 151 and 152, FIG. 2, the material beingdelivered to chutes 161-163 on the stacker, FIG. 5, as indicated byarrows 164 and 165, and then being fed horizontally by means of the feedconveyor 166 to a discharge chute I70 whereupon the material isdelivered as indicated by arrow 171 onto the longitudinal conveyor 12.The conveyor 12 may be of the endless type with its active run movingfrom left to right as viewed in FIG. I as to deliver the material to atransfer tower from which the material may travel in the direction ofarrow 181 along a conveyor system 182 for delivery of the material tobarges or other transportation means.

The arms 240 and 241 of the probe means measure the amount and directionof relative displacement between the position of alignment of thedischarge region 147 and receiving region 148 and the transducers 250and 270 respectively generate the error signal in response to themeasured displacement. The coaction between the arms 240, 241 along withthe transducer and the probe 233 provide a position-indicating means fordetermining the relative displacement of the machine 120 and stacker 19from a predetermined relative position in which the discharge andreceiving regions are in alignment for transfer of material.

While the operation has been discussed with the direction of thereclaimer or material-handling device 120 being varied with respect tothe stacker l9, and the speed of the stacker being a slave to the speedof the reclaimer, the speed and direction of the reclaimer 120 could bevaried in response to the error signals so that the movement of thereclaimer was a slave to the stacker. Furthermore, the stacker could bea slave to the reclaimer for both longitudinal and transverse error byvarying its speed and the angular position of the boom 42 in response tothe error signals.

l claim as my invention:

1. The method of retrieving material from a stockpile to which it hasbeen supplied by means of a stacker system including a conveyorextending along the length of the stockpile, and an associatedself-propelled stacker movable along the conveyor to distribute materialfrom successive points along the length of the conveyor to correspondingsuccessive points along the length of the stockpile, said methodcomprising driving a self-propelled material-retrieving machinelongitudinally of the stockpile to retrieve material therefrom,

moving the stacker along said conveyor and mechanically conveyingmaterial from the retrieving machine to the stacker for depositionthereby onto said conveyor, and

controlling the speed of movement of the stacker so as to be slaved tolongitudinal movement of the retrieving machine and to move in steptherewith, and controlling steering of the retrieving machine so as tobe slaved to the path of the stacker along said conveyor, to maintainsubstantially a material-receiving relationship of the stacker to theretrieving machine during movement thereof along the stockpile, therebyto transfer material from successive points along the length of thestockpile to corresponding successive points along the length of saidconveyor.

2. Apparatus for handling material comprising a selfpropelledmaterial-handling device including means for gathering material and aconveyor means for receiving the material and conveying the material toa discharge region;

a conveyor device including a material-receiving region, conveying meansto transport the material from said receiving region to a dischargepoint, means for moving the material receiving region to be in alignmentwith the discharge region for receiving material therefrom as thematerial-handling device moves and gathers material; and

a position indicating means having a reference member mounted on one ofsaid devices, and displacement-measuring means mounted on the otherdevice operably engaging said reference member for measuring therelative displacement of said regions from a position of alignment, saidmeasuring means including means for generating an error signal for therelative displacement to indicate the amount and direction of therelative displacement between said regions from said position ofalignment so that the speed and direction of movement of the devices canbe adjusted to return the regions into alignment.

3. Apparatus for reclaiming material from a stockpile comprising;

a self-propelled reclaimer having conveyor means for supplying materialreclaimed thereby to a material discharge region; a self-propelledstacker movable along a fixed longitudinal path offset from thestockpile during a reclaimin pass, said stacker having a longitudinalconveyor exten mg for the length of the stockpile, said stacker havingmaterial transfer means movably mounted therealong with an inlet fordisposition in operative relationship with the conveyor means of thereclaimer to receive material from the discharge region thereof andhaving an outlet for discharge of material to the longitudinal conveyor,thereby to transfer the material continuously during a reclaiming passfrom the stockpile to the longitudinal conveyor via the materialtransfer means of the stacker, and

probe means carried by the stacker and the reclaimer and coacting tomechanically define a predetennined cooperating relationship between thestacker and reclaimer wherein the discharge region of the reclaimer iscentered relative to the inlet of material transfer means, said probemeans sensing relative displacement of the discharge region from acenter position with respect to the inlet and providing an error signalfor both longitudinal and transverse displacement from the centerportion with said error signal indicating necessary corrections in thespeed of the reclaimer and the stacker to correct for any longitudinaldisplacement and changes in the direction of movement of the reclaimerand positioning of the material transfer means to correct for anytransverse displacement.

4. Apparatus according to claim 3 with one of said probe meanscomprising a transverse movement sensing arm movable in response torelative transverse movement of the reclaimer and stacker, and atransducer coupled to the sensing arm and responsive to movement thereofto generate a transverse error signal.

5. Apparatus according to claim 3 with one of said probe meanscomprising a longitudinal movement sensing arm movable in response torelative longitudinal movement of the reclaimer and stacker, and atransducer coupled to the sensing arm and responsive to movement thereofto generate a longitudinal error signal.

6. Apparatus according to claim 3 with one of said probe meanscomprising a transverse movement sensing arm movable in response torelative transverse movement of the reclaimer and stacker, a transducercoupled to the transverse movement sensing arm and responsive tomovement thereof to generate a transverse error signal, and alongitudinal movement-sensing ann movable in response to relativelongitudinal movement of the reclaimer and stacker, and a transducercoupled to the longitudinal movement-sensing arm and responsive tomovement thereof to generate a longitudinal error signal, and the otherof said probe means comprising a reference member disposed generallyvertically and retained in the verti' cal disposition with substantialforce, the sensing arms being mounted for pivotal movement in generallyhorizontal planes, and spring means urging said arms to engage thegenerally vertically disposed reference member, the spring meansexerting a lesser force on the sensing arms than said substantial forceso that the vertically extending reference member maintains itsgenerally vertical disposition in actuating said sensing arms over apredetermined range of angular positions of the sensing arms.

7. Apparatus according to claim 6 wherein further spring means retainsthe generally vertically disposed reference member in generally verticalorientation but accommodates disengagement of the vertically disposedreference member from the sensing arms when the sensing arms reach thelimit of their angular movement.

1. The method of retrieving material from a stockpile to which it hasbeen supplied by means of a stacker system including a conveyorextending along the length of the stockpile, and an associatedself-propelled stacker movable along the conveyor to distribute materialfrom successive points alOng the length of the conveyor to correspondingsuccessive points along the length of the stockpile, said methodcomprising driving a self-propelled material-retrieving machinelongitudinally of the stockpile to retrieve material therefrom, movingthe stacker along said conveyor and mechanically conveying material fromthe retrieving machine to the stacker for deposition thereby onto saidconveyor, and controlling the speed of movement of the stacker so as tobe slaved to longitudinal movement of the retrieving machine and to movein step therewith, and controlling steering of the retrieving machine soas to be slaved to the path of the stacker along said conveyor, tomaintain substantially a material-receiving relationship of the stackerto the retrieving machine during movement thereof along the stockpile,thereby to transfer material from successive points along the length ofthe stockpile to corresponding successive points along the length ofsaid conveyor.
 2. Apparatus for handling material comprising aself-propelled material-handling device including means for gatheringmaterial and a conveyor means for receiving the material and conveyingthe material to a discharge region; a conveyor device including amaterial-receiving region, conveying means to transport the materialfrom said receiving region to a discharge point, means for moving thematerial receiving region to be in alignment with the discharge regionfor receiving material therefrom as the material-handling device movesand gathers material; and a position indicating means having a referencemember mounted on one of said devices, and displacement-measuring meansmounted on the other device operably engaging said reference member formeasuring the relative displacement of said regions from a position ofalignment, said measuring means including means for generating an errorsignal for the relative displacement to indicate the amount anddirection of the relative displacement between said regions from saidposition of alignment so that the speed and direction of movement of thedevices can be adjusted to return the regions into alignment. 3.Apparatus for reclaiming material from a stockpile comprising; aself-propelled reclaimer having conveyor means for supplying materialreclaimed thereby to a material discharge region; a self-propelledstacker movable along a fixed longitudinal path offset from thestockpile during a reclaiming pass, said stacker having a longitudinalconveyor extending for the length of the stockpile, said stacker havingmaterial transfer means movably mounted therealong with an inlet fordisposition in operative relationship with the conveyor means of thereclaimer to receive material from the discharge region thereof andhaving an outlet for discharge of material to the longitudinal conveyor,thereby to transfer the material continuously during a reclaiming passfrom the stockpile to the longitudinal conveyor via the materialtransfer means of the stacker, and probe means carried by the stackerand the reclaimer and coacting to mechanically define a predeterminedcooperating relationship between the stacker and reclaimer wherein thedischarge region of the reclaimer is centered relative to the inlet ofmaterial transfer means, said probe means sensing relative displacementof the discharge region from a center position with respect to the inletand providing an error signal for both longitudinal and transversedisplacement from the center portion with said error signal indicatingnecessary corrections in the speed of the reclaimer and the stacker tocorrect for any longitudinal displacement and changes in the directionof movement of the reclaimer and positioning of the material transfermeans to correct for any transverse displacement.
 4. Apparatus accordingto claim 3 with one of said probe means comprising a transverse movementsensing arm movable in response to relative transverse movement of thereclaimer and stacker, and a transducer couplEd to the sensing arm andresponsive to movement thereof to generate a transverse error signal. 5.Apparatus according to claim 3 with one of said probe means comprising alongitudinal movement sensing arm movable in response to relativelongitudinal movement of the reclaimer and stacker, and a transducercoupled to the sensing arm and responsive to movement thereof togenerate a longitudinal error signal.
 6. Apparatus according to claim 3with one of said probe means comprising a transverse movement sensingarm movable in response to relative transverse movement of the reclaimerand stacker, a transducer coupled to the transverse movement sensing armand responsive to movement thereof to generate a transverse errorsignal, and a longitudinal movement-sensing arm movable in response torelative longitudinal movement of the reclaimer and stacker, and atransducer coupled to the longitudinal movement-sensing arm andresponsive to movement thereof to generate a longitudinal error signal,and the other of said probe means comprising a reference member disposedgenerally vertically and retained in the vertical disposition withsubstantial force, the sensing arms being mounted for pivotal movementin generally horizontal planes, and spring means urging said arms toengage the generally vertically disposed reference member, the springmeans exerting a lesser force on the sensing arms than said substantialforce so that the vertically extending reference member maintains itsgenerally vertical disposition in actuating said sensing arms over apredetermined range of angular positions of the sensing arms. 7.Apparatus according to claim 6 wherein further spring means retains thegenerally vertically disposed reference member in generally verticalorientation but accommodates disengagement of the vertically disposedreference member from the sensing arms when the sensing arms reach thelimit of their angular movement.